Accumulated Other Comprehensive Income (Loss) - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Amounts reclassified from AOCI
Foreign currency derivative gains, net	$ (593,210)	$ (518,572)	$ (1,130,800)	$ (1,000,599)
Total before tax	(129,358)	(128,640)	(180,840)	(211,744)
Tax expense	48,925	49,070	63,495	80,708
Total, net of tax	(80,433)	(79,570)	(117,345)	(131,036)
Total reclassifications for the period	1,085	1,412	1,748	806
Derivatives designated as hedging instruments under ASC 815 | Foreign currency derivative gains, net
Amounts reclassified from AOCI
Total reclassifications for the period	(298)	(542)	(1,051)	(2,191)
Derivatives designated as hedging instruments under ASC 815 | Interest rate derivative losses, net
Amounts reclassified from AOCI
Total reclassifications for the period		768		587
Derivatives designated as hedging instruments under ASC 815 | Amount reclassified from accumulated other comprehensive income (loss)
Amounts reclassified from AOCI
Total before tax	(480)	367	(1,692)	(2,577)
Tax expense	182	(141)	641	973
Total, net of tax	(298)	226	(1,051)	(1,604)
Derivatives designated as hedging instruments under ASC 815 | Amount reclassified from accumulated other comprehensive income (loss) | Foreign currency derivative gains, net
Amounts reclassified from AOCI
Foreign currency derivative gains, net	(480)	(868)	(1,692)	(3,521)
Derivatives designated as hedging instruments under ASC 815 | Amount reclassified from accumulated other comprehensive income (loss) | Interest rate derivative losses, net
Amounts reclassified from AOCI
Interest rate derivative losses, net	0	1,235	0	944
Actuarial loss
Amounts reclassified from AOCI
Amortization of defined benefit plan items	2,228	1,915	4,456	3,830
Prior service cost
Amounts reclassified from AOCI
Amortization of defined benefit plan items	60	57	120	114
Defined benefit pension
Amounts reclassified from AOCI
Amortization of defined benefit plan items	2,288	1,972	4,576	3,944
Tax benefit	(898)	(747)	(1,765)	(1,493)
Total reclassifications for the period	1,390	1,225	2,811	2,451
Short-term investments
Amounts reclassified from AOCI
Total reclassifications for the period	(7)	(39)	(12)	(41)
Short-term investments | Amount reclassified from accumulated other comprehensive income (loss)
Amounts reclassified from AOCI
Realized gain on sales of investments, net	(12)	(58)	(20)	(61)
Total before tax	(12)	(58)	(20)	(61)
Tax expense	5	19	8	20
Total, net of tax	$ (7)	$ (39)	$ (12)	$ (41)